1. Field of the Invention
This invention relates to a process for automatic control of a straightening process for a material to be straightened, such as sheet metal, strips, sections, pipes and, in particular, for wire-like or multiwire-like objects to be straightened, in a straightening apparatus or a levelling machine having at least one straightening roller, adjustable with an actuator.
2. Description of Prior Art
In order to eliminate buckling of objects to be straightened, non-rotary roller straightening apparatus or levelling machines are employed. Due to the level-sefting of the straightening rollers in relation to one another, disposed in two rows in a mutually offset manner in at least one straightening plane, the objects to be straightened are subjected to alternating bends during their passage. The quantity and magnitude of the alternating bends should be selected so that entry curvatures of objects to be straightened are eliminated over an entire length of the objects to be straightened.
Predetermining a number of alternating bends, and a magnitude of the alternating bends, is set in practice more or less intuitively according to the experience of the person operating the straightening apparatus using level-seftings of the straightening rollers. Changing the set parameters of the individual straightening rollers is thus performed by visual contact with the exiting material to be straightened until satisfactory straightness is attained.
From Guedcke W., xe2x80x9cSimulation of the Wire Straightening Processxe2x80x9d Wire Industry, Volume 63, No. 752, Aug. 1, 1996, modelling and simulation of wire straightening processes is known. Such modelling aims to discover the most ideal conditions for a straightening process and discloses specifications for conducting a straightening process. However, a specialist is required for adapting the pre-set process cycle to the actual conditions with regard to the tolerances of the respective objects to be straightened, which is attempted by adjusting the straightening rollers and by taking measurements after interrupting the straightening process.
From German Patent Reference DE 195 03 850 C1 a non-rotary straightening apparatus for bending machines with an integrated measuring device is known. In the straightening apparatus, in a direction in which material is passing through, at least one material bending measuring device, in which there is at least one measuring path for a lengthwise predetermined material section, is disposed behind at least one straightening mechanism. Thus, along the measuring path, there is at least one mechanical and/or electronic and/or optical sensor, determining the extent of the bend and its orientation, in which context signals are generated by the sensor device, representing the measured bend of the material section, and the signals are used to adjust an adjusting gear accordingly.
The measuring device of the known straightening apparatus operates according to a principle of curvature detection in terms of a Three-Point-Method, supplying correct results only for objects to be straightened, which are cut into sections, or for immobile objects to be straightened, for example if the objects to be straightened are free from exterior forces and moments, neglecting gravity. If the curvature of the discharged objects to be straightened is not constant over a length of the measuring path, the measuring result is further influenced by the length of the measuring path.
The straightening process is interrupted due to the required immobilization of the objects to be straightened. The immobilization and renewed setting into motion affects the result of the curvature measurements and necessitates changes which have an effect on a quality of the straightening process. Checking the setting is thus only possible by renewed immobilization of the straightening apparatus, i.e. continuous monitoring and adjusting while the objects to be straightened are moving or during straightening, is not possible.
It is one object of this invention to provide a process which virtually permits an immediate, automatic adaptation of the setting to continuously measured data of respective objects to be straightened of at least one straightening roller of a straightening apparatus or a levelling machine, without interrupting the straightening process.
This object is attained by a process having the characteristics described in this specification and in the claims.
Preferred embodiments of this invention are based on the principle of modelling a straightening process, which is to be automated, in a preparatory phase, using mathematical-physical laws, setting up a simulation program and performing a calculus of parameters with the simulation program with varying product data, in particular the material characteristics and/or the dimensions of the objects to be straightened. This phase may be considered as xe2x80x9cofflinexe2x80x9d. Due to product and/or process data measured continuously during the straightening process, i.e. without immobilizing the objects to be straightened, the adjustment of the straightening apparatus or the levelling machine, required in order to attain the desired product quality, is performed very quickly xe2x80x9conlinexe2x80x9d, integrating the results of the calculus of parameters. The change of the setting is performed objectively and in a determined manner. The measured product and/or process data are also used in order to check the set up model as well as the simulation program and to change them, if necessary. Objectivity replaces subjective experience judgement by the eye of the person operating the straightening apparatus or levelling machine. This not only simplifies the process, performing it automatically, but it also enhances the quality.